1. Field of the Invention
The present invention relates to a method and an apparatus for sterilizing water for eating and drinking, waste water discharged from a hydroponic system/fish hatchery, and the like.
2. Description of the Related Art
To remove microbes such as bacteria, mold and protozoa contained in water for eating and drinking such as tap water stored in, for example, a reservoir, a method has conventionally been employed which cleans up water by disposing a porous filter material capable of collecting the microbes in a running water channel, and securely capturing the microbes in the filter material.
In another method that has been employed in addition to the above method, electrodes are inserted into water for eating and drinking to perform electrolysis, whereby chlorine or ozone is generated, and by its sterilizing function, the microbes contained in water for eating and drinking are killed.
On the other hand, in the hydroponic system, crops planted in a cultivation bed have been properly grown by circulating a nutrient liquid prepared by dissolving fertilizer and manure in water at a rate suitable for crop cultivation to the cultivation bed. However, the interior of the cultivation bet to which the nutrient liquid has been circulated is an environment suitable for the propagation of pathogenic fungi such as fusarium fungi (a kind of mold). If the propagation of fusarium fungi occurs in the cultivation bed, crop roots are damaged, which kills the crops. Therefore, a device has been employed which is constructed to sterilize pathogenic fungi contained in the nutrient liquid by heating the nutrient liquid with a heater, or by ultraviolet rays or ozone contained in a light-transmissive jacket in the circulation channel of the nutrient liquid.
The above filter material receives and collects the microbes in fine holes formed on its surface. Accordingly, the microbes cannot securely be captured unless the microbes clash on the surface of the filter material or pass through its vicinity. Consequently, a limitation has been placed on the effect of securely capturing the microbes.
Since the microbes are securely captured in such a filter material as described above, a saturation state is reached in sooner or later to discharge the microbes into the running water channel. Accordingly, it can be contrived that the securely captured microbes are killed by heating the filter material, but some microbes have resistance to heat, and hence, to assure the effect of sterilization, the filter material must be heated to a relatively high temperature.
In addition, the nutrient liquid has been heated to sterilize the pathogenic fungi propagated in the cultivation bed in the hydroponic system, but since the plants are killed if the heated nutrient liquid is directly used as it is, a cooling device is necessary to cool the heated nutrient liquid. Consequently, there has been a problem that a large amount of energy must be used to heat and cool the nutrient liquid. Furthermore, when the pathogenic fungi contained in the nutrient liquid is sterilized by using ultraviolet rays or ozone, there has been another problem that the concentrations of iron and manganese contained in the nutrient liquid decrease.
The present invention has been developed to solve the foregoing conventional technical problems, and objects of the present invention are to provide a method and an apparatus for water treatment which can greatly improve the effect of removing microbes contained in water for eating and drinking or waste water, and a hydroponic system using the same.
According to a first aspect of the present invention, there is provided a method for water treatment comprising a first treatment step of dipping a pair of electrodes and a conductor capable of collecting at least microbes in a running channel of water to be treated, and applying a positive potential to the conductor and applying negative potentials to the electrodes to adsorb the microbes on the conductor; a second treatment step of stopping the flow of the water to be treated after an end of the first treatment step, and increasing the potentials applied to the conductor and the electrodes to start the electrolysis of the water to be treated while the polarities of the potentials applied to the conductor and the electrodes are maintained intact in the presence of the water to be treated; and a third treatment step of stopping the application of the potential to the conductor after an end of the second treatment step, and applying a positive potential to one of the pair of electrodes and applying a negative potential to the other of the electrodes in the presence of the water to be treated.
According to a second aspect of the present invention, there is provided a method for water treatment comprising a first treatment step of dipping a pair of electrodes and a conductor capable of collecting at least microbes in a running channel of water to be treated, and applying a positive potential to the conductor and applying negative potentials to the electrodes to adsorb the microbes on the conductor; a second treatment step of stopping the flow of the water to be treated after an end of the first treatment step, reversing the polarities of the potentials applied to the conductor and the electrodes in the presence of the water to be treated, and increasing the potentials applied to the conductor and the electrodes to start the electrolysis of the water to be treated; and a third treatment step of stopping the application of the potential to the conductor after an end of the second treatment step, and applying a positive potential to one of the pair of electrodes and applying a negative potential to the other of the electrodes in the presence of the water to be treated.
According to a third aspect of the present invention, there is provided an apparatus for water treatment comprising a pair of electrodes dipped in a running channel of water to be treated; a conductor dipped in the running channel of the water to be treated, the conductor being capable of collecting at least microbes; and a controller capable of controlling the application of potentials to each of the electrodes and the conductor, and capable of controlling the flow of the water to be treated. In this case, the controller executes a first treatment step of applying a positive potential to the conductor in a flow state of the water to be treated, and negative potentials to the electrodes to adsorb the microbes on the conductor, a second treatment step of stopping the flow of the water to be treated after an end of the first treatment step, and increasing the potentials applied to the conductor and the electrodes to start the electrolysis of the water to be treated while the polarities of the potentials applied to the conductor and the electrodes are maintained intact in the presence of the water to be treated, and a third treatment step of stopping the application of the potential to the conductor after an end of the second treatment step, and applying a positive potential to one of the pair of electrodes and applying a negative potential to the other of the electrodes in the presence of the water to be treated.
According to a fourth aspect of the present invention, there is provided an apparatus for water treatment comprising a pair of electrodes dipped in a running channel of water to be treated; a conductor dipped in the running channel of the water to be treated, the conductor being capable of collecting at least microbes; and a controller capable of controlling the application of potentials to each of the electrodes and the conductor, and capable of controlling the flow of the water to be treated. In this case, the controller executes a first treatment step of applying a positive potential to the conductor in a flow state of the water to be treated, and negative potentials to the electrodes to adsorb the microbes on the conductor, a second treatment step of stopping the flow of the water to be treated after an end of the first treatment step, reversing polarities applied to the conductor and the electrodes in the presence of the water to be treated, and increasing the potentials applied to the conductor and the electrodes to start the electrolysis of the water to be treated, and a third treatment step of stopping the application of the potential to the conductor after an end of the second treatment step, and applying a positive potential to one of the pair of electrodes and applying a negative potential to the other of the electrodes in the presence of the water to be treated.
The method or the apparatus for water treatment of the present invention further comprises a treatment step of discharging the water to be treated, in which the conductor and the electrodes are dipped, after an end of the third treatment step.
In the method or the apparatus for water treatment of the present invention, the conductor is a porous body.
In the method or the apparatus for water treatment of the present invention, the conductor is made of a carbon fiber.
In the method or the apparatus for water treatment of the present invention, the carbon fiber of the conductor includes precious metal added thereto, the precious metal being one selected from palladium, platinum, iridium, and tantalum.
In the method or the apparatus for water treatment of the present invention, in the third treatment step, chlorine and/or ozone is generated at one of the pair of electrodes, and active oxygen is generated at the other of the electrodes.
In the method or the apparatus for water treatment of the present invention, each of the electrodes includes precious metal added thereto, the precious metal being one selected from palladium, platinum, iridium, and tantalum.
According to a fifth aspect of the present invention, there is provided a hydroponic system for cultivating plants by supplying a nutrient liquid to a cultivation bed, comprising a path for recirculating a secondary nutrient liquid discharged from the cultivation bed to the same cultivation bed; and the foregoing water treatment apparatus provided in the path.